Reversing rheostat



N0V- 21, 1944 E. N. LlGHTFooT Erm. 2,353,132

REVERS ING RHEOSTAT Filed 001;. 7, 1943 Patented Nov. 2l, 1944 REVERSINGRHEOSTAT Edwin N. Lightfoot, Wauwatosa, and Theodore F.

Rosing, Whitelsh Bay, Wis.,

assignors to Cutler-Hammer, Inc., Milwaukee, Wis., a corporation ofDelaware Application October 7, 1943, Serial No. 505,266

14 Claims. (Cl. 201-62) This invention relates to improvements inrheostats of the reversing type.

A primary object of the invention is to improve and simplify theconstruction andoperation of rheostats of the aforementioned character.

Another object is to provide a simple form of rheostat which is operableto regulate and reverse the current through a load circuit from fullpositive to full negative through any desired number of steps, includingcomplete interruption of said load' circuit at an intermediate point onthe rheostat corresponding to substantially zero potential.

Another object is to provide a reversing rheostat which is adapted to bepower operated, subject to selective manual control; or alternativelyadapted for direct manual operation at will, as in the event of failureof the power operating means.

Another object is to provide an intermittent and reversing type ofsolenoid operating mechanism of novel form.

Another and more specific object is to provide for remote manualpushbutton control of said solenoid operating mechanism.

Another object is to provide a reversing rheostat embodying a common setof resistance sections electrically connected with a correspondingnumber of contact segments, the contact segments being so arranged as tobe traversed by a pair of Contact brushes operable simultaneously inopposite directions.

Anotherobject is to provide such a rheostat affording a maximum numberof steps of resistance variation with a minimum number of resistancesections.

Another object is to provide novel means for manually adjustingr orpreselecting the speed of operation of the reversing rheostat.

Various other objects and advantages of the invention will hereinafterappear.

The accompanying drawing illustrates schematically and diagrammaticallya preferred embodiment of our invention; it being'understood that theembodiment illustrated is susceptible of modification in respect ofcertain structural details thereof Without departing from the scope ofthe appended claims.

In the drawing, Figure 1 is a schematic and diagramma-tic illustrationof a reversing rheostat embodying our invention.

Fig. 2 is, a diagrammatic illustration of the form and arrangement ofcertain of the parts .shown in Fig. l, and showing in detail certainadditional elements of the timing mechanism, and

Fig. 3 is a fragmentary diagrammatic illustration, with the contactbrushes in their neutral or off position, and showing one brush in stag'gered or offset relationship to the other, whereby the two'brushes areadapted to engage the several successive contact segments in alternatesequence instead of simultaneously, thus substantially doubling thenumber of resistance gradations afforded by the rheostat.

Referring to Fig. 1, the numeral 5 designates a winding in suitable loadcircuit through which it is desired to eiect a full positive or fullnegative flow of current, or any desired value of positive or negativecurrent; the transition from positive to negative now of current, orvice versa, being effected in each case when the current is at a minimumor substantially zero value. In the device herein illustrated provisionis made for completely interrupting the flow of current at thetransition point of minimum value of the positive or negative currentflow.

The winding 5 may be assumed to represent the eld coil of a generatoremployed in a degaussing system. Line Ll and L2 represent a suitablesource of current supply for coil 5, and the numerals 6H, 6b designateresistances to which lines L1 and L2 are respectively connected at `thepoints 6c and 6d. The yterminals and 5b of coil 5 are respectivelyconnected by flexible conduc tors 'l and B to contact brushes 9 and I0;the latter in the respective positions thereof shown in Fig. l providingfor a full positive flow of current through said coil, said circuitextending from line L1 through point 6c and brush 9, conductor 1 throughpoint 5a and coil 5, and through point 5b, conductor 8, brush I0 andpoint 6d to line L2.

As best illustrated in Fig. 3, resistances 6- and 6b are divided intoany desired number of sections 6", the adjacent ends or terminals ofeach two sections 6 being electrically connected to one of themultiplicity of contact blocks or segments Il. In the diagrammaticillustration in Fig. 3 the resistance sections lie are shown interposedbetween the pairs of contact segments II, whereas actually said segmentsII are in practice located quite close to each other, so that each brush9-or I0 will engage the next adjacent segment prior to disengagementthereof from the presently engaged segment in each direction of movementof said brushes. Ihe contact segments Il are spaced the desired distancefrom each other by interposing suitable insulating plates or blocks (notshown) therebetween, the

resistance sections being terminally connected to the spaced contactsegments II in a manner to afford proper clearance for brushes 9 and I8.

The groups 6a and B1? (Fig. 1) of resistance sections 6e (Fig. 3) arepreferably separated a substantial distance from each other, as by meansof an insulating block or spacer I2, so thatl at approximately themid-length of the complete range of travel of the brushes 9 and i0 bothof the same will be disengaged from all of the contact segments il (seeFig. 3). As will be apparent from Figs. 1 and 3, when contact brushes 9and il) are engaged'respectively with the contact segments Il, Il atopposite ends of block I2 all of the resistance sections Ie will beincluded in circuit in series with coil 5, whereby the current throughthe latter is reduced to its minimum value; and in practice thearrangement is preferably such as to provide substantially zeropotential across the Vterminals of coil 5 under the condition justmentioned. Also it will be understood that the direction of current flow(positive or negative) through coil 5 will depend upon Whether brushes 9and I il are respectively engaged with the contact segments Il at theright-hand and left-hand sides of block I2 (see Fig. 3) to provide apositive flow, or with those at the left-hand and right-hand sides ofsaid block to provide a negative ow.

Any suitable means (not shown) may be pro vided for manuallyinterrupting the supply of current from lines L1, L2. Assumingcompletion of the circuit from the source of supply through lines L1,L2, and with the various elements of the system in the positions thereofshown in Fig. 1, it will be apparent that coil 5 is subjected to thefull positive potential of lines L1, L2 as aforedescribed. As shown, thecontact brush 9 is carried by a nut 9a which is adapted to travel upon arotatable threaded shaft I3 having suitable fixed bearings I4 and I5;brush 9 being insulated from nut 9a in any suitable manner, as indicatedat 3b. Also attached to n-ut 9a, but insulated therefrom as shown at 9,is an element Sid the end portion 9e of which acts in the positionthereof illustrated to effect opening of a limit switch i6, the bridgingcontactor Iiia of which is normally biased to its closed position by acompression spring I1. With contactor I6a thus disengaged from thestationary contacts of limit switch i6 the contact brushes 9 and I0cannot be driven by the power operated means beyond the extremepositions thereof illustrated. I

However, the power operated means may be utilized, under control of oneof the manually operated push buttons hereinafter described, to eifectstep by step movement of contact brushes 9 and I9 jointly toward or totheir other respective extreme positions. Thus the contact brush I E! iscarried by a nut Ilia, but insulated from the latter as shown atA Illb;the nut IIJa being adapted for cooperative engagement with a rotatablethreaded shaft I8 having suitable xed bearings I9 and 29. Also attachedto nut Illa, but

' insulated therefrom as shown at IIlc. is an element id the end portionllie of which acts, in the opposite extreme position of contact brush l0from that illustrated, to eifect opening of a limit switch 2|, theVbridging contactor 2la of which is normally biased to the closedposition thereof illustrated, as by means of compression spring 22.

The power operating means for contact brushes 2 and Ill comprises a pairof relatively small gears 23 and 24 keyed or otherwise rigidly connectedto the reduced end portions of shafts I3 and I8, said gears beingarranged to mesh continuously with a relatively larger gear 25positioned therebetween. Gear 25 is rigidly attached to one end of ashaft 26 which is rotatably supported in suitable bearings (not shown).Shaft 26 projects outwardly from gear 25 and has rigidly attachedthereto a pair of like toothed ratchet wheels 21, 21. Said wheels 21 arereversely arranged with respect to each other, so that the teeth, marked21a, of one are arranged to be engaged by a pawl 28a, carried by thecore of a solenoid 28, the coil of which is designated by numeral 281.Thus upon energization of coil 281 pawl 28a is moved upwardly from thenormal position thereof shown in Fig. 3 into engagement with one of theteeth 212, thereby effecting a predetermined degree of clockwiserotation of shaft 26 and gear wheel 25, with consequent counterclockwiserotation of gears 23 and 24 and of the respective shafts I3 and I8associated with the latter.

Inasmuch as shaft I3 is provided with a yrighthand thread and shaft I8is provided with a lefthand thread such clockwise rotation thereof willresult in downward movement of brush 9 (Fig, 1i and upward movement ofbrush I0 to increase in a step by step manner the number of sections ofthe resistances 6a and 6b included in the circuit of coil 5, pendingattainment of the minimum value of the positive current at thetransition point I2 of the rheostat, whereupon the minimum value ofnegative current is first applied to coil 5, such value being graduallyincreased until full negative current is applied when brush 9 is in itslower extreme position and brush I9 is in its upper extreme position.

When brush ID has reached the extreme position thereof last mentionedthe end portion IIII,e of element IQd associatedwith nut Illa will haveengaged and opened contactor 2 Ia of limit switch 2| to preventovertravel of the brushes III and 9 to insure against interruption ofthe circuit of coil 5 under such conditions. n

With brush I in its upper extreme position and brush 9 in its lowerextreme position (Fig. 1l. or with said brushes in any of theirrespective intermediate positions, simultaneous movement of brush 9upwardly and of brush I9 downwardly may be effected by intermittentenergization of coil 29b of solenoid 29, the core of which carries apawl 2Sa adapted for engagement with the teeth, marked 21h, of theright-hand ratchet wheel 21 in Fig. 2. Upon each upward movement of pawl292' gear 25 is rotated to a predetermined degree in a counterclockwisedirection, with consequent clockwise rotation of shafts I3 and I8 forthe purpose just mentioned.

The cores of solenoids 28 and 29 are respectively biased toward thedisengaged positions thereof shown in Fig. 2, as by means of a pair ofcoiled tension springs 39 and 3I attached to downward extensions 28 and29; said extensions being respectively pivotally connected at 32a and32b to oppositely extending arms of a lever 32, which is pivotallysupported at its mid-length, as by means of a pin 33. The intermediateor pivotal supporting portion of lever 32 is enlarged as shown at 32C,and said enlarged portion is provided with a downwardly facingdouble-inclined cam surface or 'notch 32d, which is adapted, in theintermediate or neutral position of lever 32, to accommodate the upperend of a stud or pin 34a attached to a switch contactor 34. Contactor 34is pivoted at `31510, and is normally biased out of engagement with itsassociated stationary contact 34, as by means of a, coiled compressionspring 34d. The

.bridged byv contactor 35",

asco-,rsa

arrangement is such that upon upward movement of either core 29 or 29the double-inclined cam surface 32d`will act upon stud 34l to effectengagement of contactor 34 with stationary contact 34.

Operation of the system willy now be described with particular referenceto the diagram of Fig. l. With the various elements in the respectivepositions illustrated, whereinA coil 5 is subjected to the full positivecurrent from lines L1` and L2, step by step movement of brush 9downwardly and of brush I9- upwardly, to decrease the value of thepositive current, may be effected by manually depressing and holding thepushbutton 35, whereby its normally open stationary contacts 35a are iThis completes an energizing circuit for the coil 29" of solenoid 29,

said circuit extending from line L1 by conductor 38 and a suitable fuseor similar protective device 3T, by conductor 38 through the normallyclosed contacts 39111 of a relay 39 (the operating coil of which isdesignated by numeral 39") by conductor 40 through the contacts 2|a oflimit switch 2| (which is then in its normally closed position, asillustrated), by conductor 4I to and through said coil 29", by conductor42 through said pushbutton contacts 35a and contactor 35", thence byconductor 43 through the normally closed contacts 44c and contactor 44"of a second pushbutton switch 44, and by conductors 45 and 46 throughfuse 41 and conductor 48 to line L2.

Upon energization of coil 29" in the manner just described` the pawl 29ais moved upwardly to effect a predetermined degree of counterclockwiserotation of shaft 26 and the parts carried thereby, with consequentclockwise rotation of shafts I3 and I8 to effect downward movement ofbrush 9 and upward movement. of brush l0. It may be assumed that suchstep of movement of brushes: 9 and I0 simultaneously will only result inincluding oney of the sections i5e within the circuit of coil 5f, todecrease to a predetermined degree the value of positive currentsupplied to coil 5.

Upon such upward movement of pawl 29" the lever 32 (Fig. 2) issimultaneously rotated counterclockwise to such a degree that theleft-hand inclined surface of notch 32d will act upon stud 34u t0 effectengagement of contactor 34 with stationaryy contact 34. As shown in Fig.1, this will complete an energizing circuit for the operating r coil 39"of relay 39, which circuit extends from line L1 by conductor 36 throughfuse` 31, conductors 49 and 50 through said coil 39", conductor 5I'through contact 3l!c and contactor 34, and by conductor 52 to line L2.The normally closed contacts 39i of relay 39 are thus opened to effectinterruption o1. the aforedescribed circuit of coil 29" of solenoid 29,with consequent retraction of pawl 29a and lever 32 to the neutralpositions thereof shown in Fig. 2, whereby contactor 34 is disengagedfrom contact 34c to interrupt` the energizing circuit of` coil 39".

In the absence of anyy additional elements such tially zero value.

loop containing it and coil 39" to maintain the relay contacts open fora predetermined period of time. By thus delaying the reclosure ofcontacts 39i of relay 39A the number of upward or operating strokes ofpawl 29a per unit of time may be substantially reduced, to therebycorrespondingly reduce the rate of change in the value of currentsupplied to coil 5.

We also prefer to provide a rheostat 54 connected in said loop in serieswith condenser 53; the contactor 55 of said rheostat being manuallyadjustable to provide for variation of the rate of charging of condenser53, and to correspondingly vary the total charge of the latter duringthe normal period of energization of coil 39". In this manner the periodduring which contacts 39'il of relay 39 are held open afterdisengagement of contactor 34 from contact 34c may be varied throughouta relatively wide range, to thereby provide. a, correspondingly widerange of variation i'n the rate of change of the value of current'supplied to coil 5-. Thus if rheostat contactor 55 1s moved toward theleft to decrease the value of resistance 54 in circuit the rate ofcharging of condenser 53 will be increased to maintain coil 39"energized for a longer period; and the opposite effect results frommovement of contactor 55 toward the right. 'I'he range of variation inthe rate of change in value of current in coil 5 may of course bemodified by substitution of a condenser and/or rheostat 54 of differentvalue or caliber.

Although I have illustrated a slidable contactor type of rheostat 54 itwill be apparent that I may employ any other suitable method of varyingthe value of the timing resistance, as, for example, a group ofresistance sections with taps in combination with a exible connectorassociated with said taps to short circuit any desired number of theresistance sections.

If the pushbutton 35 is manually held in its depressed position the pawl29a will be intermittently moved upwardly to effect simultaneousdownward movement of brush 9 and upward movement of brush l0 at a ratedetermined by the adjustment of rheostat contactor 55, each suchmovement of brushes 9 and I0 jointlybeing adapted to effect inclusion inthe positive current circuit of coil 5 an additional section 6 of theresistance, until just prior to the mid-length of the total range oftravel of the two brushes when all of the resistance sections 6e will beincluded in such circuit, to thereby reduce the positive current throughcoil 5 to its minimum or substan- Thereafter one or both of the brushes9 and I0 will move onto the insulating block f2 to insure completeinterruption of the circuit of coil 5 (see Fig. 3).

Upon continuous downward movement of brush 9 and upward movement ofbrush ID the brush 9 will engage the first contact segment Il at theleft-hand side of block I2 (Fig. 3) while brush I0 is still engaged withthe first contact segment H at the right-hand side of said block, thuseffecting completion of the negative current circuit of coil 5 with allof the resistance sections 6" included therein, whereby said negativecurrent is initially of minimum or'substantially zero value. Thereafterthe resistance sections E." will be exclude-d in sequence from thenegative` current circuit,v until at the lowermost position of brush 9and the uppermost position of brush l0 (as controlled by the operationof limit switch 2l as aforedescribed) all of the resistance sections 5ewill be excluded from manually adjusted to either increase or decreasethe rate of movement of the brushes, to thereby provide for decreasingor increasing the period of time required for change from one characterand/ or Value to another of the current supplied to coil 5.

With brush 9 in its lowermost position and brush I9 in its uppermostposition, or with said brushes jointly in any other than the respectiveextreme positions thereof shown in Fig. l, simultaneous movement ofbrush 9 upwardly and brush IU downwardly may be effected by manuallydepressing and holding pushbutton 44 so that its contactor 441 isengaged with stationary contacts 44a (the pushbutton 35, of course,having been released to permit return thereof to its normal positionillustrated). Such depression of pushbutton 44 will complete anenergizing circuit for the coil 26b of solenoid 28, which circuit may betraced from line L2 by conductor 48 through fuse 41, by conductors 46and 56, stationary contacts 35c and contactor 35h of pushbutton switch35, by conductor 51 through stationary contacts 44a and contacter 44h ofpushbutton switch 44, by conductor 58 through the coil 28b of solenoid28, by conductor 59 through the normally closed contacts of limit switchi6, by conductor 4U through contacts 39a of relay 39, by conductors 38and 4S through fuse 31, and by conductor 36 to line L1.

In practice we prefer to provide a fixed resistance 69 and a condenser6| connected in series with each other across the terminals of coils 28band 29h. If the limit switches IB and 2l are both closed (as in anyintermediate positions of brushes 9 and i9) upon release of the lastactive pushbutton switch 35 or 44 a discharge circuit through theresistance Ell, condenser 2l and the inactive coil 28h or 29", as thecase may be, is provided for the last active coil 29b or 28h. This hasthe eiect of minimizing arcing at the contacts of pushbuttons 35 or 44and at the contacts 39a of relay 39.

As shown in Figs. 1 and 2 We prefer to nonrotatably attach to the outerend of shaft 26 a manually rotatable knob 62, whereby manual adjustmentor movement of brushes 9 and l0 may be eiiected at Will entirelyindependently of the power operating means of the rheostat. This featureis of importance in the event of failure or derangement of any part ofthe power operating means. Knob '62 is also useful for enabling manualpresetting of the brushes 9 and i0 of the rheostat atk the desiredpositions thereof prior to completion of the rheostat circuit from thesource of current supply which is here represented by lines L1, L 2.

' While we have herein illustrated a rheostat of the series type inwhich the circuit from the line through coil 5 is opened just prior tomovement of brushes 9 and S) to their neutral or intermediate position,it will be apparent to those skilled in the art that what is commonlyknown as a potentiometer connection may be employed, where preferred forsome specic installation, by substituting for insulating block I2 aconductive block which will maintain the circuit through the resistor6e, 6b from one line to the other.

Furthermore, where a conductive block is used such block has the furtherfunction of short-circuiting coil 5 before the direction of current flowtherein is reversed, thereby aording a discharge path for any energy inthe magnetic field, if it is found desirable to provide some means forabsorbing such energy; thus affording what is commonly known as adischarge circuit. Such operation will take place at a time when thecurrent is reduced substantially to zero so that the magnetic energy isrelatively small but nevertheless requires some means to guard againstarcing or insulation failure consequent upon high discharge voltages.

We claim:

l. In a reversing rheostat, in combination, a single set of resistancesections, a single set of xed spaced contact segments respectivelyelectrically connected with said resistance sections, the end contactsegments of said set being respectively connected to opposite poles of asource of current supply, a pair of Contact brushes common to saidcontact segments and adapted to cooperate therewith, means for effectingmovement of said contact brushes jointly in opposite directionsrespectively throughout the total length of said set of contactsegments, a translating device including a coil the terminals of whichare re spectively connected with said contact brushes, whereby in oneeXtreme position of the respective brushes said coil is subjected to thefull positive potential of said source of current supply and in theother eXtreme position of the respective brushes said coil is subjectedto the full negative potential of said source of current supply, andwherebyat the midpoint of the total range of movement of said brushesjointly they are subjected to substantially zero potential wherefore nocurrent iiows through said coil.

2. In a reversing rheostat, in combination, a single set of resistancesections, a single set of Xed spaced contact segments respectivelyelectrically connected with said resistance sections, the end contactsegments of said set being respectively connected to opposite poles of asource of current supply, a pair of contact brushes common to saidcontact segments and adapted to cooperate therewith, means for effectingmovement of said contact brushes jointly in opposite directionsrespectively throughout the total length of said set of contactsegments, a translating device including a coil the terminals of whichare respectively connected with said contact brushes, whereby in oneextreme position of the respective brushes said coil is subjected to thefull positive potential of said source of current supply and in theother extreme position of the respective brushes said coil is subjectedto the full negative potential of ,said source of current supply,whereby at the midpoint of the total range of movement of said brushesjointly they are subjected to substantially zero potential wherefore nocurrent ows through said coil, and power operated means reversible atwill for effecting movement of said brushes jointly toward and fromeither of their respective extreme positions.

3. In a reversing rheostat, in combination, a single set of resistancesections, a single set of xed spaced contact segments respectivelyelectrically connected with `said resistance sections, the end contactsegments of said set being respectively connected to opposite poles of asource of current supply, a pair of contact brushes common to saidcontact segments and adapted to cooperate therewith, means for effectingmovement of said contact brushes jointlyin opposite directionsrespectively, a translating device including a coil the terminals ofwhich are respectively connected with said contact brushes, whereby inone extreme position of the respective brushes said coil is subjected tothe full positive potential of said source of current supply and in theother extreme position of the respective brushes said coil is subjectedto the full negative potential of said source of current supply, wherebyat the midpoint of the total range of movement of said brushes jointlythey are subjected to Vsubstantially zero potential wherefore no currentflows through said coil, power operated means reversible at will foreffecting movement of said `brushes jointly toward and from either oftheir respective extreme positions, said last mentioned means includinga pair of oppositely threaded parallel rotatable shafts, traveling nutson said shafts in a predetermined relationship to each other, saidbrushes being attached to the respective nuts for movement with thelatter, a third shaft geared to said shafts first mentioned, a pair ofoppositely toothed ratchet wheels non-rotatably attached to said thirdshaft, a solenoid including a coil, a core and a pawl associated witheach ratchet wheel, and a pair of pushbutton switches selectivelyoperable to control intermittent energization of the respective solenoidcoils.

4. In a reversing rheostat, in combination, a single set of resistancesections, a single set of xed spaced contact segments respectivelyelectrically connected with said resistance sections, the end contactsegments of said set being respectively connected to Opposite poles of asource of current supply, a pair of contact brushes common to saidcontact segments and adapted to cooperate therewith, means for effectingmovement; of said Contact brushes jointly in opposite directionsrespectively, a translating device including a coil the terminals ofwhich are respectively connected with said contact brushes, whereby inone extreme position of the respective brushes said coil is subjected tothe full posiktive potential of said source of current supply and in theother extreme position of the respective brushes said coil is subjectedto the full negative potential of said source of current supply, wherebyat the midpoint of the total range of movement of said brushes jointlythey are subjected to substantially zero potential wherefore no currentflows through said coil, power operated means reversible at will foreffecting move- 4ment of said brushes jointly Ytoward and from either oftheir respective extreme positions, said last mentioned means includinga pair of oppositely threaded parallel rotatable shafts, traveling nutson said shafts in a predetermined relationship to each other, saidbrushes being attached to the respective nuts for movement with thelatter, a third shaft geared to said shafts rst mentioned, a pair ofoppositely toothed ratchet wheels non-rotatably attached to said thirdshaft, a solenoid including a coil, a core and a pawl associated witheach ratchet wheel, a pair of pushbutton switches selectively operablemanually to provide for operating energization of one or the other ofthe solenoid coils, means comprising a cam-operated normally open switchadapted to be closed automatically upon operating movement of either ofthe solenoid cores, a normally closed electromagnetically operable relayadapted to be energized upon each closure of said last mentioned switch,said relay when opened being adapted to eifect deenergization of eitherof said solenoid coils to provide for resetting of its re- A spectivepawl and reopening of said normally open switch whereby 'the energizingcircuit of said relay is interrupted, and said relay when deenergizedeffecting reenergization of the active solenoid coil to provide arepeated operation of the pawl associated therewith.

y5. In a reversing rheostat, in combination, a single set of resistancesections, a single set of xed Vspaced contact segments respectivelyelectrically connected with said resistance sections, the end Icontactsegments of said set being respectively connected to opposite poles of asource of current supply, a pair of contact brushes common to saidcontact segments and adapted to cooperate therewith, means for effectingmovement of said contact brushes jointly in opposite directionsrespectively, a translating device including a coil the terminals ofwhich are respectively connected with sa'id contact brushes, whereby inone extreme position of the respective brushes said coil vis subjectedto the full positive potential of said source of current supply and inthe other extreme position of the respective brushes said coil issubjected to thev full negative potential of said source of currentsupply, whereby at the midpoint of the total range'of movement of saidbrushes jointly they are subjected to substantially zeropotentialwherefore no current flows through said coil, vpower operated meansreversible at will for effecting movement of said brushes jointly towardand from either of their respective extreme positions, said lastmentioned means including a pair of oppositely threaded parallelrotatable shafts, traveling nuts on said shafts in a predeterminedrelationship to each other, said brushes being attached to therespective nuts for movement with the latter, .a third shaft geared tosaid shafts first mentioned, a pair of oppositely toothed ratchet'wheelsnon-rotatably attached to said third shaft, a solenoid including a coil,a core and a pawl associated with each ratchet wheel, a pair of'pushbutton switches selectively operable manually to provide foroperating energization of one or the other of the solenoid coils, means-comprising a cam-operated normally open switch adapted to be closedautomatically upon operating movement of either of the solenoid cores, a'normally closed electromagnetically opy erable relay adapted to beenergized upon each closure of said 'last mentioned switch, said relaywhen opened being adapted to effect deenergization of either of saidsolenoid coils to provide for resetting of its respective pawl andreopening of said normally open switch whereby the energizing circuit ofsaid relay is interrupted, said relay when deenergized effectingreenergization of the active solenoid coil to provide a repeatedoperation of Athe pawl associated therewith, and adjustable meansassociated Awith said relay to delay reclosure thereof upon interruptionof its energizing circuit, whereby the `rate of movement of saidvbrushes jointly by said power operated means may be preselected.

r6. In a reversing rheostat, kin combination, a single set of'resistance sections, a single set of fixed spaced contact segmentsrespectively electrically connected with said resistance sections, theend contact segments of said set being respectively connected toopposite poles of a source of current supply, a pair of contact brushescommon to said contact segments and adapted to cooperate therewith,meanssfor effecting movement'l of said contact brushes jointly inopposite directions respectively, a translating device including a coilthe terminals of which are respectively connected with said contactbrushes, whereby in one extreme position of the respective brushes saidcoil is subjected to the full positive potential of said source ofcurrent supply and in the other extreme position of the respectivebrushes said coil is subjected to the full negative potential of saidsource of current supply, whereby at the midpoint of the total range ofmovement of said brushes jointly they are subjected to substantiallyZero potential wherefore no current ows through said coil, poweroperated means reversible at will for eiecting movement of said brushesjointly toward and from either of their respective extreme positions,said last mentioned means including a pair of oppositely threadedparallel rotatable shafts, traveling nuts on said shafts in apredetermined relationship to each other, said brushes being attached tothe respective nuts for movement with the latter, a third shaft gearedto said shafts first mentioned, a pair of oppositely toothed ratchetwheels non-rotatably attached to said third shaft, a solenoid includinga coil, a core and a pawl associated with each ratchet wheel, a pair ofpushbutton switches selectively operable manually to provide foroperating energization of one or the other of the solenoid coils, meanscomprising a .cam-operated normally open switch adapted to be closedautomatically upon operating movement of either of the solenoid cores,la normally closed electromagnetically operable relay adapted to beenergized upon each closure of said last mentioned switch, said relaywhen opened being adapted to effect deenergization of either of saidsolenoid coils to provide for resetting of its respective pawl andreopening of said normally open switch whereby the energizing circuit ofsaid relay is interrupted, said relay when deenergized eifectingreenergization of the active solenoid coil to provide a repeatedoperation of the pawl associated therewith, adjustable means associatedwith said relay to delay reclosure thereof upon interruption of itsenergizing circuit, whereby the rate of movement of said brushes jointlyby said power operated means may be preselected, and said adjustablemeans comprising a condenser and an adjustable resistance connected in aclosed loop in series with each other and with the coil of said relay toprovide for maintaining the operating energization of the latter for apredetermined period f time after interruption of the normal energizingcircuit of said relay coil.

7. In a reversing rheostat, in combination, a

single set of resistance sections, a single set ofspaced contactsegments electrically connected in series relationship to each otherthrough the medium of the respective resistance sections, said contactsegments being arranged in a line, the contact segments at opposite endsof said line being respectively connected to opposite poles of asuitable source of current supply, a pair of contact brushes common toand jointly cooperable with said contact segments throughout the lengthof said line, a translating device including a coil whose terminals arerespectively connected with said brushes to provide for passage ofcurrent to said coil from said source of supply, the arrangement beingsuch that when said brushes are respectively engaged in one relationwith opposite end contact segments of said line said coil will besubjected to the full positive potential of said source, and when saidbrushes are respectively reversed in position with respect to said endcontact segments said coil will be subjected to the full negativepotential of said source, of means for effecting movement of saidbrushes simultaneously from' each of their respective extreme positionsto their other extreme positions, and vice versa, across theintermediate contact segments of the line, whereby the variation incharacter and value of said change from full positive to full negativevalue, and vice versa, of the current supplied to said coil may beeffected in increments corresponding to the resistance value or valuesof said multiplicity of resistance sections.

8. In a reversing rheostat, in combination, a multiplicity of resistancesections, contact segments electrically connected in series relationshipthrough the medium of the respective resistance sections, said contactsegments being arranged in a straight line in fixed spaced relationshipto each other, the Contact segments at opposite ends of said line beingrespectively connected to opposite poles of a suitable source of currentsupply, a pair of contact brushes movable simultaneously in oppositedirections in slidable engagement with different portions of therespective contact segments throughout the total length of said line, atranslating device including a coil whose terminals are respectivelyconnected with said brushes to provide for passage of current throughsaid coil from said source of supply, the arrangement being such thatwhen said brushes are respectively in one of their extreme positionsfull positive current is supplied to said coil and when the same arerespectively in the other of their extreme positions full negativecurrent is supplied to said coil, said brushes cooperating with saidsegments and said resistance sections to effect transition from fullpositive to full negative current in a step by step manner, includingreduction of said current to substantially zero value at the midpoint ofthe total range of travel of said brushes jointly, power operated meansfor effecting the aforementioned simultaneous opposite movement of saidbrushes in either direction throughout their total range, and associatedmeans for automatically controlling said power operated means to preventovertravel of said brushes at each of their extreme positions.

9. In a reversing rheostat, in combination, a multiplicity of stationarycontact segments arranged in a straight line in fixed spacedrelationship to each other, a multiplicityof resistance sections theterminals of which are connected to said contact segments in seriesrelationship to each other, a pair of current supply lines respectivelyconnected to the opposite end contact seg-- ments, a pair of -contactbrushes slidably engageable with said contact segments at opposite sideedges thereof, a translating device including a coil the terminals ofwhich are connected to the respective brushes, each of said contactbrushes being movable into and out of engagement with all of saidcontact segments selectively, means for effecting movement of saidcontact brushes simultaneously in opposite directions from each endcontact segment to the other, said means comprising a pair of oppositelythreaded shafts, traveling nuts on said shafts, each nut having one ofsaid brushes attached thereto for movement therewith, means foreffecting intermittent rotation of said shafts jointly in 'one directionor the other, said means comprising a third shaft and gearing betweenthe same and said shafts first mentioned, a pair of oppositely toothedratchet wheels non-rotatably attached to said third shaft, a solenoidincluding a coil, a core and a pawl associated with one 'of said ratchetWheels, said pawls being normally biased to positions alfordingclearance for the respective ratchupon intermittent energization of itscoil to efy fect step by step movement of said brushes jointly towardthe respective extreme positions thereof providing full positiveenergization of said first mentioned coil, the other solenoid whenintermittently energized being adapted to effect step by step movementof said brushes jointly toward their opposite extreme positionsproviding full negative energization of said first mentioned coil, saidbrushes at the mid-point of their complete range of travel beingsubjected to substantially zero potential so that no current will besupplied to said rst mentioned coil, and means including a pair ofpushbutton switches selectively operable manually to provide forintermittent operating energization of one or the other of saidsolenoids.

10. In a reversing rh'eostat, in combination, a multiplicity ofstationary contact segments arranged in a straight line in xed spacedrelationship to each other, a multiplicity of resistance sections theterminals of which are connected to said contact segments in seriesrelationship to each other, a pair of current supply lines respectivelyconnected to the opposite end contact segments, a pair of contactbrushes slidably engageable with said contact segments at opposite sideedges thereof, a translating device including a coil the terminals ofwhich are connected to the respective brushes, each of said contactbrushes being movable into and out of engagement with all of'saidcontact segments selectively, means for effecting movement of saidcontact brushes simultaneously in opposite directions from each endcontact segment to the other, said means comprising a pair of oppositelythreaded shafts, traveling nuts on said shafts, each nut having one ofsaid brushes attached thereto for movement therewith, means forelfecting intermittent rotation of said shafts jointlyin one directionor the other, said means comprising a third shaft and gearing betweenthe same and saidshafts first mentioned, a pair of oppositely toothedratchet wheels non-rotatably attached to said third shaft, a solenoidincluding a coil, a core and a pawl associated with each of said ratchetwheels, said pawls being normally biased to positions affordingclearance for the respective ratchet wheels, one of said solenoids beingadapted upon intermittent energization of its coil to effect step bystep movement of said,brushes jointly toward the respective extremepositions thereof providing full positive energization of said rstmentioned coil, the other solenoid when intermittentiy energized beingadapted to effect step by step movement of said brushes jointly towardtheir opposite extreme positions providing full negative energization ofsaid rst mentioned coil, said brushes at the mid-point of their completerange of travel being subjected to substantially zero potential so thatno current will be supplied to said first mentioned coil, meanscomprising a pair of pushbutton switches selectively operable manuallyto provide for operating energization of one or the other of saidsolenoids, means comprising a normally open switch adapted to be closedautomatically upon operating movement of either of said solenoid cores,a normally closed electromagnetically operable relay adapted to beenergized upon each closure of said last mentioned switch, said relaywhen opened being adapted to effect deenergization of either of saidsolenoid coils to provide for resetting of its respective pawl andreopening of said normally open switch, said switch when reopenedeffecting interruption of the energizing circuit of said relay, and saidrelay when deenergized and closed providing for reenergization of theactive solenoid coil, whereby a repeated operation of its associatedpawl is effected.

11. In a reversing rheostat, in combination, a multiplicityof stationarycontact segments arranged in a straight line in fixed spacedrelationship to each other, a multiplicity of resistance sections theterminals of which are connected to said contact segments in seriesrelationship to each other, a pair of current supply lines respectivelyconnected to the opposite end contact segments, a pair of contactbrushes slidably engageable with said contact segments at opposite sideedges thereof, a translating device including a coil the terminals ofwhich are connected to the respective brushes, each of said contactbrushes being movable into and out of engagement with all of said1contact segments selectively, means for effecting movement of saidcontact brushes simultaneously in opposite directions from each endcontact segment to the other, said means comprising a pair of oppositelythreaded shafts, traveling nuts on said shafts, each nut having one ofsaid brushes attached thereto for movement therewith, means foreffecting intermittent rotation of said shafts jointly in one directionor the other, said means comprising a third shaft and gearing betweenthe same and said shafts first mentioned, a pair of oppositely toothedratchet wheels non-rotatably attached to said third shaft, a solenoidincluding a coil, a core and a pawl associated with each of said ratchetwheels, said pawls being normally biased to positions affordingclearance for the respective ratchet wheels, one of said solenoids beingadapted upon intermittent energization of its coil to elfect step bystep movement of said brushes jointly toward the respective extremepositions thereof Aproviding full positive energization of said nrstmentioned coil, the other solenoid when intermittently energized beingadapted to effect step by step movement of said brushes jointly towardtheir opposite extreme positions providing full negative energization ofsaid first mentioned coil, said brushes at the mid-point of theircomplete range of travel being subjected to substantially zero potentialso that no current will be supplied to said first mentioned coil, meanscomprising a pair of pushbutton switches selectively operable manuallyto provide for operating energization of one 'or the other of saidsolenoids, means comprising a normally open switch adapted to be closedautomatically upon operating movement of either of said solenoid cores,a normally closed electromagnetically operable relay adapted to beenergized upon each closure of said last mentioned switch, said relaywhen opened being adapted to effect deenergization of either of saidsolenoid coils to provide for resetting of its respective pawl andreopening of said normally open switch, said switch when reopenedeffecting interruption of the energizing circuit of said relay, saidrelay when deenergized and closed providing for reenergization of theactive solenoid coil, whereby a repeated operation of its associatedpawl is effected, and adjustable means associated with said relay todelay reclosure thereof upon interruption of its energizing circuit,whereby the rate of movement of said brushes jointly by said poweroperated means may be preselected.

12. In a reversing rheostat, in combination, a multiplicity ofstationary contact segments arranged in a straight line in fixed spacedrelationship to each other, a multiplicity of resistance sections theterminals of which are connected to said contact segments in seriesrelationship to each other, a pair of current supply lines respectivelyconnected to the opposite end contact segments, a pair of contactbrushes slidably engageable with said contact segments at opposite sideedges thereof, a translatingdevice including a coil the terminals ofwhich are connected to the respective brushes, each of said contactbrushes being movable into and out of engagement with all of saidContact segments selectively, means for effecting movement of saidcontact brushes simultaneously in opposite directions from each endcontact segment to the other, said means comprising a pair of oppositelythreaded shafts, traveling nuts on said shafts, each nut having one ofsaid brushes attached -thereto for movement therewith, means for eectingintermittent rotation of said shafts jointly in one direction or theother, said means comprising a third shaft and gearing between the sameand said shafts first mentioned, a pair of .oppositely toothed ratchetwheels non-rotatably attached to said third shaft, a solenoid includinga coil, a core and a pawl associated with each of said ratchet wheels,said pawls being normally biased to positions affording clearance forthe respective ratchet wheels, one of said solenoids being adapted uponintermittent energization of its coil to eifect step by Step movement ofsaid brushes jointly toward the respective extreme positions thereofproviding full positive energization of said rst mentioned coil, theother solenoid when intermittently energized being adapted to effectstep by step movement of said brushes `jointly toward their oppositeextreme positions providing full negative energization of said rstmentioned coil, said brushes at the mid-point of their complete range oftravel being subjected to substantially zero potential so that, nocurrent will be supplied to said rst mentioned coil, means comprising apair of pushbutton switches selectively operable manually to provide foroperating energization oi one or the other of said solenoids, meanscomprising a normally open switch adapted to be closed automaticallyupon operating movement of either of said solenoid cores, a normallyclosed electromagnetically operable relay adapted to be energized uponeach closure of said last mentioned switch, said relay when opened beingadapted to eiect deenergization of either of said solenoid coils toprovide for resetting of its respective pawl and reopening of saidnormally open switch, said switch when reopened effecting interrupton ofthe energizing circuit of said relay, said relay when deenergized andclosed providing for reenergization of the active solenoid coil, wherebya repeated operation of its associated pawl is effected, adjustablemeans associated with said relay to delay reclosure thereof uponinterruption of its energizing circuit, whereby the rate of movement ofsaid brushes jointly by said 'power operated means may be preselected.,and said adjustable means comprising a condenser and a variableresistance connected in a closed loopwith the coil of said relay toinsure operating energization of the latter for a predetermined periodvof time after interruption of the normal energizing circuit thereof inthe manner aforementioned.

13. In a reversing rheostat, in combination, a multiplicity of fixedcontact segments arranged in a straight.line in spaced relationship toeach other, a pair of contact brushes on opposite sides of said contactsegments and movable simultaneously in opposite directions respectivelyfrom each extreme contact segment toward the other, a multiplicity ofresistance sections associated with said contact segments, said extremecontact segments being respectively connected with opposite poles of asource of current supply, a translating device including a winding theterminals of which are connected with the respective brushes, a pair oftraveling nuts to which said brushes are respectively attached, a pairof oppositely threaded shafts with which said nuts are respectivelyassociated, power operated electrical means common to said shafts nforeffecting rotation thereof jointly in one direction or the other, meansincluding a pair of pushbutton switches operable selectively to eiTectoperation of said power operated means in one direction or thel other,and means including a cam operated'switch and an electromagneticallyoperable relay associated with said power operated means to insureoperation thereof intermittently in each direction respectively tothereby insure movement of said brushes jointly in a step by stepmanner.

1li.` In a reversing rheostat, in combination, a multiplicity of fixedcontact segments arranged in a straight line in spaced relationship to.each other, a pair of contact brushes on opposite sides of said ContactSegments and movable simultaneously in opposite directions respectivelyfrom each extreme contact segment toward the other, a multiplicity ofresistance sections associated with said contact segments, said eXtremecontact segments being respectively connected with opposite poles of asource of current supply, a translating device including a winding theterminals of which are connected with the respective brushes, a pair oftraveling nuts to which said brushes are respectively attached, a pairof oppositely threaded shafts with which said nuts are respectivelyassociated, power operated electrical means common to said shafts lforeffecting rotation thereof jointly in one direction or the other, meansincluding ya pair of pushbutton switches' operable selectively to effectoperation of said power operated means in one direction or the other,means including a cam operated 'switch and an electromagneticallyoperable relay associated with said power operated means to insureoperation thereof intermittently in each direction respectively tothereby insure movement of said brushes jointly in a step by stepmanner, said relay having a set of normally closed contacts, a condenserand a rheostat connected in series with each other in a closed loopincluding the operating winding of said relay, said condenser1 and saidrheostat coacting with the operating winding of said relay to delayreclosure of the latter after interruption of the normal energizingcircuit of said winding by said cam operated switch, and said rheostatbeing adjustable to vary at will 4within a given range the time delayafforded by said relay.

EDWIN N. LIGHTFOOT.

THEODORE F. ROSING.

